1. Technical Field
The present invention relates to an inkjet printing machine configured to prevent unevenness of density by appropriate correction even when positional displacement of an inkjet head is generated in the main scanning direction.
2. Related Art
A full-line-type inkjet printing machine includes inkjet heads corresponding to ink colors C (cyan), M (magenta), Y (yellow), and K (black). The printing machine performs printing line by line by discharging ink from the inkjet heads while transferring a sheet in a direction perpendicular to the direction of rows of inkjet heads by using a transfer belt provided under the inkjet heads.
Some of such inkjet printing machines may have a plurality of rows of inkjet heads respectively provided along a main scanning direction for each ink color. In addition, a printing speed which is number-of-rows times as high as an inkjet printing machine having a single inkjet head row can be obtained by discharging ink sequentially from the inkjet heads. For example, an inkjet printing machine provided with two rows of inkjet heads can perform printing processing at a printing speed twice as high as an inkjet printing machine provided with a single row of inkjet heads.
In such an inkjet printing machine provided with a plurality of rows of inkjet heads respectively for each ink color, positional displacement of inkjet heads may be generated due to an installation error of an inkjet head or an impact on the machine during transportation, which may cause density unevenness in the printed image.
Patent Document 1 discloses a technique related to an inkjet printing apparatus configured to obtain, from the analysis result of recording media and discharged patterns, the amount of displacement in the sheet transfer direction (sub-scanning direction) and the nozzle row direction (the main scanning direction), correct the discharge timing in the sheet transfer direction, and correct the discharge timing by shifting the data to be printed in the nozzle row direction.
Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2014-91304